Studying non-covalent enzyme carbohydrate interactions by STD NMR.

Saturation transfer difference NMR spectroscopy is used to study non-covalent interactions between four different glycostructure transforming enzymes and selected substrates and products. Resulting binding patterns represent a molecular basis of specific binding between ligands and biocatalysts. Substrate and product binding to Aspergillus fumigatus glycosidase and to Candida tenuis xylose reductase are determined under binding-only conditions. Measurement of STD effects in substrates and products over the course of enzymatic conversion provides additional information about ligand binding during reaction. Influences of co-substrates and co-enzymes in substrate binding are determined for Schizophyllum commune trehalose phosphorylase and C. tenuis xylose reductase, respectively. Differences between ligand binding to wild type enzyme and a corresponding mutant enzyme are shown for Corynebacterium callunae starch phosphorylase and its His-334-->Gly mutant. The resulting binding patterns are discussed with respect to the possibility that ligands do not only bind in the productive mode.